Why MEP Engineers Don’t Recommend Oversized Equipment for Buildings

Michael Tobias
3 Minutes Read
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    There is a common misconception that having spare capacity is a good thing in mechanical, electrical and plumbing installations. However, professional MEP engineers recommend using optimally-sized equipment that meets your needs. In fact, oversized installations have several disadvantages, and some are not evident until a building is already in use.

    Oversized equipment is more expensive, and eventual part replacements also come with a higher price tag. You can also end up paying higher utility bills, and oversized installations are more demanding in terms of maintenance. Also, the extra capacity can actually hinder performance in some applications.

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    Oversized Equipment Is More Expensive

    Real estate development is a capital-intensive business, and costs are even higher in places like New York, New Jersey and Chicago. When MEP installations are oversized, construction projects become even more expensive and less lucrative for developers.

    Paying more makes sense for building upgrades that improve performance; some examples are LED lighting, high-efficiency heat pumps and solar power systems. However, oversized equipment just represents extra capacity that is not being used, while demanding additional maintenance.

    By working with qualified MEP engineers, you can make sure all building systems are specified with the right capacity, reducing the project costs. If there is additional capital available, you can ask consulting engineers to recommend energy efficiency measures, which is a much smarter way to use the project budget.

    Oversized Equipment Has Higher Maintenance Costs

    As you might expect, oversized MEP equipment uses larger internal components. As a consequence, part replacements are more expensive compared with equipment of optimal capacity. Reparations and replacements are rarely an issue with new equipment, especially when there is a solid warranty, but eventually you will have to assume those costs.

    In the specific case of HVAC systems, oversized equipment tends to run in shorter cycles because the desired temperature is reached faster. However, this is not a good thing: short cycles are very demanding for mechanical components, causing accelerated wear. In this case you are not only paying for expensive part replacements, but also have to purchase them earlier because their service life is reduced.

    Oversized Equipment Has Higher Operating Costs

    This issue becomes evident when buildings get their first utility bills. When MEP installations are oversized, they draw larger amounts of water, electricity and natural gas. This represents a permanent expense throughout the service life of a building. Although this issue can be minimized if equipment controls are configured properly, a better solution is to simply use MEP equipment of the right capacity.

    Oversized equipment is notorious for its high operating cost in older installations, since control systems have limited capacity or are missing completely. In these cases, a major efficiency boost is possible with a complete retrofit of building systems.

    Oversized Equipment Suffers From Performance Issues

    Contrary to popular belief, extra capacity does not lead to better performance when dealing with MEP systems in buildings. The following are some examples of how oversized equipment can achieve poor results:

    • Oversized air conditioners cool indoor areas too fast, leaving no time for humidity removal. As a result, you may end up with a cold and moist environment that feels like a refrigerator, causing discomfort and possibly health issues.
    • Excessive lighting consumes more electricity without providing any benefits - meeting the illuminance levels recommended by IESNA is enough for human visibility. In fact, excessive lighting can bother buildings occupants with glare.
    • Oversized plumbing systems cause a drastic increase in pumping power, since more water must be moved through piping.
    • Oversized water heaters consume more fuel than necessary, and occupants are exposed to burns from overheated water.
    • Oversized fans consume more electricity, and they can cause high air speeds that are uncomfortable for occupants.
    • In general, oversized mechanical equipment tends to cause high levels of noise and vibration. Noise causes discomfort and distraction, and vibration can damage many building components.

    These are just a few examples, and a longer list is possible. In a few words, oversized equipment does not perform better, and it actually causes many problems.

    Final Recommendation

    Oversized MEP installations bring additional costs and many issues, without offering any benefits in return. The best recommendation is getting in touch with professional engineers, who can design building systems of the right capacity while meeting local building codes. The resulting savings can then be used for building upgrades that actually improve performance.


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    Tags : MEP Engineering over engineering building performance

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